Logical Packet Switching Device With Switching Fabric Extended between Multiple Physical Devices

ABSTRACT

In one embodiment, a logical packet switching device has its switching fabric extended between multiple physical devices, such as, but not limited to, over one or more networks (e.g., over tunnel(s), point-to-point link(s), and/or public and/or private L2 or L3 network(s)). In particular, one embodiment extends the switching fabric between multiple different physical devices by effectively merging, at least from the perspective of ingress and/or egress line cards, a switching fabric in each of these multiple different physical devices. In this regard, an ingress lookup operation in a first physical device of one embodiment produces information which is used by the switching fabric in a different physical device to forward a packet to the appropriate egress line card in the different physical device. Further, one embodiment includes line cards which can be used to both extend the switching fabric as well as communicate with packet switching and other devices that are independent of the logical packet switching device.

TECHNICAL FIELD

The present disclosure relates generally to extending the switchingfabric of a packet switching device across a network.

BACKGROUND

The communications industry is rapidly changing to adjust to emergingtechnologies and ever increasing customer demand. This customer demandfor new applications and increased performance of existing applicationsis driving communications network and system providers to employnetworks and systems having greater speed and capacity (e.g., greaterbandwidth). In trying to achieve these goals, a common approach taken bymany communications providers is to use packet switching technology.

Accordingly, the ability to provide communications mechanisms andmethodologies that allow greater bandwidth, achieve superiorperformance, and/or offer minimal delay presents a significant challengefor designers of packet switching devices and network managers.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended claims set forth the features of one or more embodimentswith particularity. The embodiment(s), together with its advantages, maybe best understood from the following detailed description taken inconjunction with the accompanying drawings of which:

FIG. 1 illustrates a logical packet switching device configured tooperate, and/or operating, according to one embodiment;

FIG. 2A illustrates a logical packet switching device configured tooperate, and/or operating, according to one embodiment;

FIG. 2B illustrates a line card configured to operate, and/or operating,according to one embodiment;

FIG. 3 illustrates an apparatus or component configured to operate,and/or operating, according to one embodiment;

FIG. 4 illustrates a process configured to be performed, and/orperformed, in one embodiment; and

FIG. 5 illustrates a process configured to be performed, and/orperformed, in one embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS 1. Overview

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with a logical packet switching devicehaving its switching fabric extended between multiple physical devices.

One embodiment of a logical packet switching device comprises: a firstphysical device including a plurality of first ports, a first switchingfabric, and a plurality of first egress line cards; and a secondphysical device including a plurality of second ports, a secondswitching fabric, and a plurality of second egress line cards. The firstand second physical devices are each configured to extend the switchingfabric of the logical packet switching device between the first andsecond physical devices over one or more standard-protocol networkscoupled to one or more of the plurality of first ports and to one ormore of the plurality of second ports. This extending of the switchingfabric of the logical packet switching device includes: the firstphysical device sending packets including second fabric information foruse by the second switching fabric in switching corresponding packets toone or more egress line cards of the plurality of second egress linecards, and the second physical device sending packets including firstfabric information for use by the first switching fabric in switchingcorresponding packets to one or more egress line cards of the pluralityof first egress line cards.

One embodiment of a logical packet switching device comprises: a firstphysical device including a first dual purpose line card, comprising aplurality of first ports; and a second physical device including a firstdual purpose line card, comprising a plurality of second ports. Each ofthe plurality of first ports and the plurality of second ports areconfigurable to perform each function of: a first function of extendingthe switching fabric of the logical packet switching device betweenphysical devices, and a second function of communicating packets withone or more other devices that are independent of the logical packetswitching device; and wherein at least one port of the plurality offirst ports and at least one port of the plurality of second ports areeach configured to extend the switching fabric of the logical packetswitching device between the first and second physical devices; andwherein at least one port of the plurality of first ports is configuredto communicate packets with one or more other packet switching devicesthat are independent of the logical packet switching device; and whereinat least one port of the plurality of second ports is configured tocommunicate packets with one or more other packet switching devices thatare independent of the logical packet switching device.

2. Description

Disclosed are, inter alia, methods, apparatus, computer-storage media,mechanisms, and means associated with a logical packet switching devicehaving its switching fabric extended between multiple physical devices.

Note, as used herein, the term “logical packet switching device” refersto a single, coherent packet switching device with a common controlplane that has its hardware distributed among multiple differentphysical devices (e.g., racks) that are communicatively coupled toperform the switching functionality. In particular, one embodimentextends the switching fabric between multiple different physical devicesby effectively merging, at least from the perspective of ingress and/oregress line cards, a switching fabric in each of these multipledifferent physical devices.

Further, as used herein, the term “ingress” refers to the arrivaldirection in which packets are processed; while the term “egress” refersto the departure direction in which packets are processed. For example,an ingress line card/port typically refers to the line card/port onwhich a packet is received by a packet switching device, and an egressline card/port typically refers to the line card/port from which apacket will exit a packet switching device (e.g., exit the logicalpacket switching device in one embodiment). Line cards are typicallyconfigured to perform the ingress and egress capabilities.

Further note, as used herein, the term “standard-protocol networks”refers to a network that at least the layer 2 and/or layer 3 of whichconforms to an industry standard, although it may use custom extensionsas provided for in the industry standard. Examples of such networksinclude, but are not limited, to an Internet Protocol (IP) network, anIEEE-defined protocol network (e.g., 802.11, 802.3, Ethernet), aMultiprotocol Label Switching (MPLS) network, an Asynchronous TransferMode (ATM) network, and a Synchronous Optical Network (SONET). Incontrast, an example of a non-standard-protocol network would be aproprietary implementation of communication over a communication link.

Embodiments described herein include various elements and limitations,with no one element or limitation contemplated as being a criticalelement or limitation. Each of the claims individually recites an aspectof the embodiment in its entirety. Moreover, some embodiments describedmay include, but are not limited to, inter alia, systems, networks,integrated circuit chips, embedded processors, ASICs, methods, andcomputer-readable media containing instructions. One or multiplesystems, devices, components, etc. may comprise one or more embodiments,which may include some elements or limitations of a claim beingperformed by the same or different systems, devices, components, etc. Aprocessing element may be a general processor, task-specific processor,or other implementation for performing the corresponding processing. Theembodiments described hereinafter embody various aspects andconfigurations, with the figures illustrating exemplary and non-limitingconfigurations. Note, computer-readable media and means for performingmethods and processing block operations (e.g., a processor and memory orother apparatus configured to perform such operations) are disclosed andare in keeping with the extensible scope and spirit of the embodiments.Note, the term “apparatus” is used consistently herein with its commondefinition of an appliance or device.

Note, the steps, connections, and processing of signals and informationillustrated in the figures, including, but not limited to, any block andflow diagrams and message sequence charts, may typically be performed inthe same or in a different serial or parallel ordering and/or bydifferent components and/or processes, threads, etc., and/or overdifferent connections and be combined with other functions in otherembodiments, unless this disables the embodiment or a sequence isexplicitly or implicitly required (e.g., for a sequence of read thevalue, process said read value—the value must be obtained prior toprocessing it, although some of the associated processing may beperformed prior to, concurrently with, and/or after the read operation).Also note, nothing described or referenced in this document is admittedas prior art to this application unless explicitly so stated.

The term “one embodiment” is used herein to reference a particularembodiment, wherein each reference to “one embodiment” may refer to adifferent embodiment, and the use of the term repeatedly herein indescribing associated features, elements and/or limitations does notestablish a cumulative set of associated features, elements and/orlimitations that each and every embodiment must include, although anembodiment typically may include all these features, elements and/orlimitations. In addition, the terms “first,” “second,” etc. aretypically used herein to denote different units (e.g., a first element,a second element). The use of these terms herein does not necessarilyconnote an ordering such as one unit or event occurring or coming beforeanother, but rather provides a mechanism to distinguish betweenparticular units. Moreover, the phrases “based on x” and “in response tox” are used to indicate a minimum set of items “x” from which somethingis derived or caused, wherein “x” is extensible and does not necessarilydescribe a complete list of items on which the operation is performed,etc. Additionally, the phrase “coupled to” is used to indicate somelevel of direct or indirect connection between two elements or devices,with the coupling device or devices modifying or not modifying thecoupled signal or communicated information. Moreover, the term “or” isused herein to identify a selection of one or more, including all, ofthe conjunctive items. Additionally, the transitional term “comprising,”which is synonymous with “including,” “containing,” or “characterizedby,” is inclusive or open-ended and does not exclude additional,unrecited elements or method steps. Finally, the term “particularmachine,” when recited in a method claim for performing steps, refers toa particular machine within the 35 USC §101 machine statutory class.

Expressly turning to the figures, FIG. 1 illustrates logical packetswitching device 100 configured to operate, and/or operating accordingto one embodiment. As shown, logical packet switching device 100includes a first physical device 110 and a second physical device 130,which may be colocated or geographically distributed, such as, but notlimited to, being located in different building, different cities, etc.

First physical device 110 includes line cards 111 and 119 forcommunicating with other devices (e.g., packet switching device, hosts,independent of, e.g., not integral to, logical packet switching device100), switching fabric 113, and line cards 116-118 configured to extendthe switching fabric between multiple physical devices 110 and 130 oflogical packet switching device 100. Note, the switching fabric of alogical packet switching device may be extended among two, or more thantwo, logical packet switching devices as taught herein to one skilled inthe art. Further note, in one embodiment, one of more of line cards 111may have the same capability as line card 116 (e.g., also could be usedto extend the switching fabric), but is not denoted as such because theyare not configured as such in the one embodiment illustrated in FIG. 1.

Second physical device 130 includes line cards 131 and 139 forcommunicating with other devices (e.g., packet switching device, hosts,independent of, e.g., not integral to, logical packet switching device100), switching fabric 133, and line cards 136-138 configured to extendthe switching fabric between multiple physical device 110 and 130 oflogical packet switching device 100. Note, the switching fabric of alogical packet switching device may be extended among two, or more thantwo, logical packet switching devices as taught herein to one skilled inthe art. Further note, in one embodiment, one of more of line cards 131may have the same capability as line card 136 (e.g., also could be usedto extend the switching fabric), but is not denoted as such because theyare not configured as such in the one embodiment illustrated in FIG. 1.

As illustrated in relation to other devices 129 (e.g., packet switchingdevice(s), host(s)), one or more of line cards 116-118 and 136 may beused to communicate with other devices 129, in addition to extending theswitching fabric (121) of logical packet switching device 100 betweenmultiple physical devices 110 and 130 over one or more networks 125(e.g., standard-protocol networks). Also, line cards 119 and 139 may beused to communicate with other devices 129 via one or more networks 125.

As shown, the switching fabric of logical packet switching device 100 isextended (121) between multiple physical devices 110 and 130 over one ormore networks 125 (e.g., standard-protocol networks). One embodimentaccomplishes this by including in an ingress lookup result informationof first physical device 110: information which can be used by switchingfabric 133 of second physical device 130 to forward packets to anappropriate egress line card 131, 136-139 of second physical device 130.For the other direction of packet traffic between multiple physicaldevices 110 and 130, one embodiment accomplishes this by including in aningress lookup result information of second physical device 130:information which can be used by switching fabric 113 of first physicaldevice 110 to forward packets to an appropriate egress line card 111,116-119 of first physical device 110. Internally, each physical device110 and 130 typically will forward packets, that are to be sent from theother device 130 and 110, to one of their line cards 116-118 or 136-138for communicating over one or more networks 125 to the other physicaldevice 130 or 110. In one embodiment, the forwarding of packets betweenswitching fabric 113 of first physical device 110 and switching fabric133 of first physical device 130 is effectively hidden such that thereceiving switching fabric 113 or 133 forwards a received packet as ifthe packet was natively received on the corresponding physical packetswitching device 110 or 130.

FIG. 2A illustrates a packet switching device 200 (e.g., appliance,rack, router, switch) used in one embodiment. As shown, packet switchingdevice 200 includes line cards 201 and 205, each of which is configuredto: extend the switching fabric between multiple physical devices thatare part of a logical packet switching device, and/or communicate withother devices (e.g., packet switching devices, hosts). As shown, packetswitching device 200 also includes a switching fabric communicativelycoupling line cards 201 and 205, other cards 204 (e.g., service cards,blades), and a route processor 202 configured in conjunction with otherpacket switching devices(s) used to extend the switching fabric of alogical packet switching device. As known to one skilled in the art,route processor 202 is part of the control plane of packet switchingdevice 200.

FIG. 2B illustrates a line card 260 used in one embodiment. As shown,line card 260 includes multiple ports 261 which may be configured forone or more purposes (e.g., extending the switching fabric amongmultiple physical devices in a logical packet switching device,communicating with other packet switching devices and/or hosts externalto the logical or physical packet switching device including line card260). Also shown in FIG. 2B is network processor 262 (with memory andpossibly other components) that process packets for line cards 261.Thus, one embodiment uses a same packet processor 262 for processingpackets that are sent over the extended switching fabric of a logicalpacket switching device, as well as packets sent to an external deviceor host.

FIG. 3 is a block diagram of an apparatus or component 300 used in oneembodiment associated with a logical packet switching device having itsswitching fabric extended between multiple physical devices. In oneembodiment, apparatus or component 300 performs one or more processescorresponding to one of the flow diagrams illustrated or otherwisedescribed herein, and/or illustrated in another diagram or otherwisedescribed herein.

In one embodiment, apparatus or component 300 includes one or moreprocessing element(s) 301, memory 302, storage device(s) 303,specialized component(s) 305 (e.g. optimized hardware such as forperforming operations, etc.), and interface(s) 307 for communicatinginformation (e.g., sending and receiving packets, user-interfaces,displaying information, etc.), which are typically communicativelycoupled via one or more communications mechanisms 309, with thecommunications paths typically tailored to meet the needs of aparticular application. In one embodiment, apparatus or component 300corresponds to, or is part of, logical packet switching device 100 ofFIG. 1, packet switching device 200 of FIG. 2A, and/or line card 260 ofFIG. 3B.

Various embodiments of apparatus or component 300 may include more orfewer elements. The operation of apparatus or component 300 is typicallycontrolled by processing element(s) 301 using memory 302 and storagedevice(s) 303 to perform one or more tasks or processes. Memory 302 isone type of computer-readable/computer-storage medium, and typicallycomprises random access memory (RAM), read only memory (ROM), flashmemory, integrated circuits, and/or other memory components. Memory 302typically stores computer-executable instructions to be executed byprocessing element(s) 301 and/or data which is manipulated by processingelement(s) 301 for implementing functionality in accordance with anembodiment. Storage device(s) 303 are another type of computer-readablemedium, and typically comprise solid state storage media, disk drives,diskettes, networked services, tape drives, and other storage devices.Storage device(s) 303 typically store computer-executable instructionsto be executed by processing element(s) 301 and/or data which ismanipulated by processing element(s) 301 for implementing functionalityin accordance with an embodiment.

FIG. 4 illustrates a process performed in one embodiment of a logicalpacket switching device. Processing begins with process block 400. Inprocess block 402, a packet is received on an ingress port of an ingressline card.

As determined in process block 403, if the packet is not received fromthe same logical packet switching device (e.g., over an extendedswitching fabric of the logical packet switching device), then inprocess block 404, the received packet is processed, which includesperforming an ingress lookup operation on an ingress forwardinginformation base (FIB) to identify a corresponding egress line card andegress port of the logical packet switching device, which can be on thesame or a different physical device of the logical packet switchingdevice.

As determined in process block 405, if the packet is to be sent to aline card on the same physical device, then in process block 406, thereceived packet and information for use by the switching fabric arecommunicated to the switching fabric for sending the received packet tothe egress line card (on the same physical device) identified by theingress lookup operation.

Otherwise, as determined in process block 405, the received packet andswitching information is to be communicated over the extended switchingfabric to an egress line card on a different physical device of thelogical packet switching device. In process block 410, selected is aline card and port on the same physical device that is being used toextend the switching fabric to a different device including thedestination egress line card (and egress port) of the logical packetswitching device. One embodiment uses a load balancing and/or other datarouting technique (e.g., based on traffic type, priority, etc.) inselecting and/or distributing packets among line cards and/or ports (andeffectively which network links) for communicating to the differentphysical device of the logical packet switching device. In process block412, the packet and switching information is communicated to theswitching fabric of the same physical device for communicating thisinformation to the egress line card for forwarding over the extendedswitching fabric to a different physical device of the logical packetswitching device.

Otherwise, as determined in process block 403, the packet was receivedfrom a different physical device of the logical packet switching device.Then, in process block 420, the encapsulation of the received packet isremoved to reveal the originally received packet and the switchingfabric information (identified by a previous ingress lookup operation),and these are communicated to the switching fabric for sending to theegress line card on the same physical device.

In process block 428, the received packet and switching information iscommunicated to an egress line card on the same physical device.Processing of the flow diagram of FIG. 4 is complete as indicated byprocess block 429.

FIG. 5 illustrates a process performed in one embodiment, which beginswith process block 500. In process block 502, a packet and switchingfabric information are received on an egress line card from theswitching fabric on the same physical device. As determined in processblock 503, if the packet is not to be sent over the extended switchingfabric of the logical packet switching device, then in process block504, the packet is processed, typically including an egress lookupoperation, with the packet being sent out the corresponding port of theegress line card to a device (e.g., packet switching device, host)external to the logical packet switching device. Otherwise, in processblock 506, the packet and switching fabric information is encapsulatedin another packet formatted for communication across one or morenetworks (e.g., over tunnel(s), point-to-point link(s), and/or publicand/or private L2 or L3 network(s)) to another physical packet switchingdevice of the logical packet switching devices that includes the linecard and/or port identified by the original ingress lookup operation.Processing of the flow diagram of FIG. 5 is complete as indicated byprocess block 509.

In view of the many possible embodiments to which the principles of ourdisclosure may be applied, it will be appreciated that the embodimentsand aspects thereof described herein with respect to thedrawings/figures are only illustrative and should not be taken aslimiting the scope of the disclosure. For example, and as would beapparent to one skilled in the art, many of the process block operationscan be re-ordered to be performed before, after, or substantiallyconcurrent with other operations. Also, many different forms of datastructures could be used in various embodiments. The disclosure asdescribed herein contemplates all such embodiments as may come withinthe scope of the following claims and equivalents thereof.

1. A logical packet switching device, comprising: a first physicaldevice including a plurality of first ports, a first switching fabric,and a plurality of first egress line cards; and a second physical deviceincluding a plurality of second ports, a second switching fabric, and aplurality of second egress line cards; wherein the first and secondphysical devices are each configured to extend a switching fabric of thelogical packet switching device between the first and second physicaldevices over one or more standard-protocol networks coupled to one ormore of the plurality of first ports and to one or more of the pluralityof second ports; and wherein said extending of the switching fabric ofthe logical packet switching device includes: the first physical devicesending packets including second fabric information for use by thesecond switching fabric in switching corresponding packets to one ormore egress line cards of the plurality of second egress line cards, andthe second physical device sending packets including first fabricinformation for use by the first switching fabric in switchingcorresponding packets to one or more egress line cards of the pluralityof first egress line cards.
 2. The logical packet switching device ofclaim 1, wherein the second fabric information includes theidentification of an egress line card of the plurality of second egressline cards; and wherein the first fabric information includes theidentification of an egress line card of the plurality of first egressline cards.
 3. The logical packet switching device of claim 1, whereinthe second fabric information includes the identification of an egressline card of the plurality of second egress line cards and a port on theegress line card; and wherein the first fabric information includes theidentification of a particular egress line card of the plurality offirst egress line cards and a port on the particular egress line card.4. The logical packet switching device of claim 1, wherein a particularegress line card of the plurality of first egress line cards includes: afirst particular port of the plurality of first ports, and a secondparticular port of the plurality of first ports; wherein the logicalpacket switching device is configured to communicate packets via thefirst particular port to the second physical device for said extendingthe switching fabric of the logical packet switching device; wherein thelogical packet switching device is configured to communicate packetscommunicated via the second particular port to one or more devicesindependent of the logical packet switching device.
 5. The logicalpacket switching device of claim 4, wherein said one or more devicesindependent of the logical packet switching device include packetswitching devices.
 6. The logical packet switching device of claim 1,wherein a particular egress line card of the plurality of first egressline cards includes a network processor for processing packets,including packets communicated via a first particular port of theplurality of first ports to the second physical device for saidextending the switching fabric of the logical packet switching device,and including packets communicated via a second particular port of theplurality of first ports to one or more devices independent of thelogical packet switching device.
 7. The logical packet switching deviceof claim 6, wherein said one or more devices independent of the logicalpacket switching device include packet switching devices.
 8. The logicalpacket switching device of claim 1, wherein said one or morestandard-protocol networks include: an Internet Protocol (IP) network,an IEEE-defined protocol network, or a Multiprotocol Label Switching(MPLS) network.
 9. The logical packet switching device of claim 1,wherein said extending the switching fabric of the logical packetswitching device between the first and second physical devices isperformed over point-to-point communications links.
 10. The logicalpacket switching device of claim 1, wherein the first physical device isa first rack, and the second physical device is a second rack.
 11. Thelogical packet switching device of claim 10, wherein the first andsecond racks are located in physically different buildings.
 12. Thelogical packet switching device of claim 1, wherein the first and secondphysical devices are located in physically different buildings.
 13. Alogical packet switching device, comprising: a first physical deviceincluding a first dual purpose line card, with the first dual purposeline card comprising a plurality of first ports; and a second physicaldevice including a second dual purpose line card, with the second dualpurpose line card comprising a plurality of second ports; wherein eachof the plurality of first ports and the plurality of second ports areconfigurable to perform a first function of extending the switchingfabric of the logical packet switching device between the first and thesecond physical devices, and a second function of communicating packetswith one or more other devices that are independent of the logicalpacket switching device; and wherein at least one port of the pluralityof first ports and at least one port of the plurality of second portsare each configured to extend the switching fabric of the logical packetswitching device between the first and second physical devices; whereinat least one port of the plurality of first ports is configured tocommunicate packets with one or more other packet switching devices thatare independent of the logical packet switching device; and wherein atleast one port of the plurality of second ports is configured tocommunicate packets with one or more other packet switching devices thatare independent of the logical packet switching device.
 14. The logicalpacket switching device of claim 13, wherein the first physical deviceis a first rack, and the second physical device is a second rack. 15.The logical packet switching device of claim 13, wherein said at leastone port of the plurality of first ports and said at least one port ofthe plurality of second ports are each coupled to one or morestandard-protocol networks over which the switching fabric of thelogical packet switching device is extended.
 16. The logical packetswitching device of claim 13, wherein said one or more standard-protocolnetworks include: an Internet Protocol (IP) network, an IEEE-definedprotocol network, or a Multiprotocol Label Switching (MPLS) network. 17.A method, comprising: extending, by a first physical device of a logicalpacket switching device and a second physical device of the logicalpacket switching device, a switching fabric of the logical packetswitching device across one or more standard-protocol networks betweenone or more first ports of the first physical device and one or moresecond ports of the second physical device; wherein said extending bythe first physical device includes performing, for each first particularpacket of a plurality of first particular packets: an ingress lookupoperation on said first particular packet to identify first forwardinginformation including the identification of a first particular egressline card of the second physical device, and communicating said firstparticular packet and the first forwarding information to the secondphysical device, with the second physical device switching said firstparticular packet to the first particular egress line card based on saidcommunicated first forwarding information.
 18. The method of claim 17,wherein said extending by the second physical device includesperforming, for each second particular packet of a plurality of secondparticular packets: an ingress lookup operation on said secondparticular packet to identify second forwarding information includingthe identification of a second particular egress line card of the firstphysical device, and communicating said second particular packet and thesecond forwarding information to the first physical device, with thefirst physical device switching said second particular packet to thesecond particular egress line card based on said communicated secondforwarding information.
 19. The method of claim 17, wherein said firstforwarding information includes an identification of a first particularport of the first particular egress card; and wherein said switching ofsaid first particular packet by the second packet switching deviceincludes communicating said first particular packet to the firstparticular port.
 20. The method of claim 19, wherein said extending bythe first physical device includes the first packet switching devicesending packets of the plurality of first packets from at least oneport, on a particular egress line card of the first physical device, ofsaid one or more first ports; and wherein the method includes: the firstphysical device communicating, via one or more additional ports on theparticular egress line card, packets to one or more devices independentof the logical packet switching device.
 21. The method of claim 20,comprising: processing of third particular packets by a packet processoron the particular egress line card; wherein said third particularpackets include packets sent from said at least one port of said one ormore first ports and said one or more additional ports.
 22. The methodof claim 17, wherein said one or more standard-protocol networksinclude: an Internet Protocol (IP) network, an IEEE-defined protocolnetwork, or a Multiprotocol Label Switching (MPLS) network.